• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.488-491
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• 2000

Bi-2223/Ag superconducting wires have been mainly prepared by a powder-in-tube method. The drawing and the rolling are main processes to increase the core density and wire length. In the fabrication of long wire, especially, the drawing should be precisely controlled to assure the filament homogeneity. In this paper, the influences of drawing die angle, bearing length and reduction ratio on the sausaging and the critical current density of the wire are investigated. Single cored and multi-filamentary wires are fabricated by PIT method with different conditions. The core densities and sausaging in the wires are investigated and are discussed regarding their relationship to the I$_{c}$. It was made clear that the geometry of drawing die is sensitively dependent on the sausaging. The improvement of I$_{c}$ was achieved by reducing the die angle and high core density.ity.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.111-114
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• 2010

In the attrition reactor for the American Society for Testing and Materials (ASTM) D5757-95, the attrition characteristics of catalysts for water gas shift reaction were investigated. The effects of attrition characteristics of low temperature shift catalysts (LTS) and high temperature shift catalysts (HTS) on fluidization phenomena and average particle size were investigated and compared with the attrition characteristics of sand particles. The particle size of catalysts was decreased and particle size distribution in attrition tube was changed due to the effect of gas injection. About 40~50 wt% samples of original catalyst particles were entrained and lost. The amount of fly ash of LTS catalyst was less than that of HTS. Also, the weight of entrained particles which had original particle size of $212{\sim}300{\mu}m$ was lower than any other cases.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.301-308
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• 2011

The diametral creep of pressure tubes (PTs) in CANDU (CANada Deuterium Uranium) reactors is one of the principal aging mechanisms governing the heat transfer and hydraulic degradation of the heat transport system (HTS). PT diametral creep leads to diametral expansion, which affects the thermal hydraulic characteristics of the coolant channels and the critical heat flux (CHF). The CHF is a major parameter determining the critical channel power (CCP), which is used in the trip setpoint calculations of regional overpower protection (ROP) systems. Therefore, it is essential to predict PT diametral creep in CANDU reactors. PT diametral creep is caused mainly by fast neutron irradiation, temperature and applied stress. The objective of this study was to develop a bundle position-wise linear model (BPLM) to predict PT diametral creep employing previously measured PT diameters and HTS operating conditions. The linear model was optimized using a genetic algorithm and was devised based on a bundle position because it is expected that each bundle position in a PT channel has inherent characteristics. The proposed BPLM for predicting PT diametral creep was confirmed using the operating data of the Wolsung nuclear power plant in Korea. The linear model was able to predict PT diametral creep accurately.

• Progress in Superconductivity
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• v.3 no.1
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• pp.130-133
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• 2001

A multifilamentary Bi-2223 HTS tape for superconducting power applications was studied through the fabrication of 250-meter long tapes by the PIT(powder in tube) process. To fabricate continuous long wire, a drawing machine, a two-drum bull block and a rolled tape winding machine were developed. Especially, 250-meter long tapes were heat treated in the shape of pancake coil to reduce the heat affect zone and to achieve the high critical current. Engineering critical current density was improved through both the enhancements of critical current density by control of thermal process and the increase of filling factor by using thin Ag alloy sheath tubes less than 1.5 mm in thickness. We have made successfully 250-meter long 37 filamentary tapes with high filling factor up to 31 % employing the modified drawing and rolling technique. The critical current of 250-meter long tapes with pancake coil type was measured by transport method at self-field up to 250 gauss of center field. The measured values, based on the transport critical current at self-field, $I_{c}$ -B characteristics and magnetic field analysis, are 34 A of I$_{c}$ and 4.0 $kA/\textrm{cm}^2$ of $J_{e}$ at 250 m, 77 K, and 0 T. We also have achieved the 56 A of I$_{c}$ and 7.0 $0 kA/\textrm{cm}^2$ of$ J_{e}$ in short tapes at 77K, self-field, and 1$mutextrm{V}$/cm.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.760_761
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• 2009

초전도 시스템에서 전류를 공급하는 역할을 하는 전류리드는 없어서는 안 될 핵심 부품이다. Powder-in-tube(PIT) 법으로 제작한 1세대(1G) 고온초전도 선재보다 열전달특성이 나쁜 2세대(2G) 고온초전도 선재를 이용하여 고온초전도 전류리드를 제작하였다. 사용한 선재는 미국 AMSC사 선재이다. 초전도 자석으로의 열침입을 최소화하기 위해 지지구조물은 GFRP를 사용하였고 금속연결부는 무산소동을 사용하였다. 2G 선재 6가닥을 사용하여 제작한 전류리드는 액체질소 온도에서 I-V 특성을 평가한 결과 약 400 A급 전류리드도 사용 가능하다고 판단되었으며, 열전달 특성을 측정하기 위해 무냉매형 특성평가장치를 사용하였는데, 77 K과 7 K 사이에서 약 50 mW정도 였다. 본 논문에선 2G 고온초전도 선재를 사용하여 제작한 전류리드의 전기적 열적 특성에 대해 논의하고자 한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.474-477
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• 2002

We performed a continuous heat treatment experiment for long Si$_2$Sr$_2$CaCuO$_{x}$ (Bi2212) superconductor tapes on copper substrates. A precursor that contains a mixture of Bi$_2$O$_3$, SrCO$_3$, and CaCO$_3$ powders was prepared and screen-printed on Cu tapes. The screen- printed tapes were thermally treated by consecutive processes with various temperature settings using an air-filled tube furnace. The diffraction patterns and the microstructures of the high temperature superconductor thick films were analyzed by X-ray diffractometry (XRD) and optical Microscopy respectively, and the critical temperatures of the superconducting thick films were measured. The critical temperatures of the superconducting films were measured to be about 77K, and the films'crystallographic c-axes were confirmed to be normal to the film surfaces by XRD and morphology observation. We also observed that the thick superconducting layer is formed and aligned on the copper substrate via partial melted state that consists of a liquid phase and a secondary phase.e.

• International journal of advanced smart convergence
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• v.8 no.2
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• pp.102-108
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• 2019

Big data was associated with three key concepts, volume, variety, and velocity. Securities and investment services produce and store a large data of text/numbers. They have also the most data per company on the average in the US. Gartner found that the demand for big data in finance was 25%, which was the highest. Therefore securities and investment companies produce the largest data such as text/numbers, and have the highest demand. And insurance companies and credit card companies are using big data more actively than banking companies in Korea. Researches on the use of big data in securities and investment companies have been found to be insignificant. We surveyed 22 major securities and investment companies in Korea for activating big data. We can see they actively use AI for investment recommend. As for big data of securities and investment companies, we studied open API. Of the major 22 securities and investment companies, only six securities and investment companies are offering open APIs. The user OS is 100% Windows, and the language used is mainly VB, C#, MFC, and Excel provided by Windows. There is a difficulty in real-time analysis and decision making since developers cannot receive data directly using Hadoop, the big data platform. Development manuals are mainly provided on the Web, and only three companies provide as files. The development documentation for the file format is more convenient than web type. In order to activate big data in the securities and investment fields, we found that they should support Linux, and Java, Python, easy-to-view development manuals, videos such as YouTube.

• Progress in Superconductivity and Cryogenics
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• v.25 no.2
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• pp.14-18
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• 2023

Superconducting layers deposited on the metal substrate using the pulsed laser deposition process (PLD) play a crucial role in exploring new applications of superconducting wires and enhancing the performance of superconducting devices. In order to improve the superconducting property and increase the throughput of superconducting wire fabricated by pulsed laser deposition, high temperature heating device is needed that provides high temperature stability and strong durability in high oxygen partial pressure environments while minimizing performance degradation caused by surface contamination. In this study, new heating device have been developed for PLD process that deposit and growth the superconducting material continuously on substrate using reel-to-reel transportation apparatus. New heating device is designed and fabricated using iron-chromium-aluminum wire and alumina tube as a heating element and sheath materials, respectively. Heating temperature of the heater was reached over 850 ℃ under 700 mTorr of oxygen partial pressure and is kept for 5 hours. The experimental results confirm the effectiveness of the developed heating device system in maintaining a stable and consistent temperature in PLD. These research findings make significant contributions to the exploration of new applications for superconducting materials and the enhancement of superconducting device performance.